- CAS
- 1132-61-2; sodium salt often 71119-22-7
- pKa, literature
- 7.18 at 25 °C
- Form
- Solid
MOPS sits between MES and HEPES. RNA gels are the usual reason to ask for it. The sodium and hemisodium salts dissolve closer to neutral and are separate rows.
What it is
MOPS (3-(N-morpholino)propanesulfonic acid) is a Good's buffer with a useful range of about pH 6.5–7.9. It is the propane homolog of MES, binds most metals weakly, and has no primary amine, which makes it compatible with formaldehyde-containing RNA gels.
Where it is used
- Denaturing formaldehyde-agarose RNA gels: 1× MOPS buffer is commonly 20 mM MOPS, 5 mM sodium acetate and 1 mM EDTA at pH 7.0.
- MOPS-SDS running buffer for Bis-Tris protein gels, typically 50 mM MOPS, for mid- to high-molecular-weight proteins.
- Defined bacterial media such as MOPS minimal medium, where about 40 mM MOPS replaces phosphate as the main buffer.
- Some yeast, plant and mammalian culture work near neutral pH.
Handling tips
- Titrate the free acid with NaOH; the sodium salt dissolves closer to neutral.
- MOPS solutions turn yellow when autoclaved or left in light. Filter-sterilize and store dark; a slight yellow tint in an RNA running buffer is widely tolerated, a dark one is not.
- For RNA work, use nuclease-free water and dedicated glassware.
What to specify when ordering
- Free acid (1132-61-2) or sodium / hemisodium salt (often 71119-22-7).
- Solid or ready 10× solution, and whether RNase-free testing is required.
- Grade and pack size. Compare it with HEPES on the buffer page.
Properties and storage
- Formula
- C7H15NO4S
- Molecular weight
- 209.26
- Appearance
- White crystalline powder
- Solubility
- Freely soluble in water
- Storage
- Room temperature, dry; keep solutions dark and discard if yellow
- Typical packs
- 25 g, 100 g, 500 g
Typical literature values. The batch COA / SDS governs.
Before you inquire
Is a ready MOPS solution listed?
Solid salt and ready solution can both be inquired. For a solution, give the concentration, pH and whether it is a 10× RNA running buffer.
Why has my MOPS buffer turned yellow?
Light exposure or autoclaving causes gradual degradation. A pale straw color is common in used RNA buffers; a dark yellow or brown solution should be replaced.
Is MOPS the same as MOPSO?
No. MOPSO carries an extra hydroxyl group and has a lower pKa, about 6.87 at 25 °C.
Pack sizes and catalogue numbers
CTH10014-1KG
Prices on request; lead time confirmed on the quotation.
Request a quote for MOPS
Name the salt form, grade, pack size and use. We compare sources and reply.
Send an inquiryFor research or industrial use only. Not for human or animal diagnosis or treatment, and not for drug or food use. Grade, pack size and lead time follow the supplier batch COA / SDS. Figures on this site are general industry references, not a factory specification.